alloc.c

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#include <stdlib.h>
#include <errno.h>
#include <limits.h>
#include "byte.h"
#include "alloc.h"
 
#define ALIGNMENT 16 /* XXX: assuming that this alignment is enough */
#define SPACE 4096   /* must be multiple of ALIGNMENT */
#define space ((char *)realspace)
 
typedef union { 
        char irrelevant[ALIGNMENT]; 
        double d; 
} aligned;
 
static aligned realspace[SPACE / ALIGNMENT];
static unsigned int avail = SPACE; /* multiple of ALIGNMENT; 0<=avail<=SPACE */
 
// /*@null@*//*@out@*/char *alloc(unsigned int n) -- old style
void *alloc(unsigned int n) 
{
  char *x;
 
/* Guninski exploit + patch from Qualys (CVE-2005-1513) */
 
  if (n >= (INT_MAX >> 3)) {
    errno = ENOMEM;
    return 0;
  }
 
  n = ALIGNMENT + n - (n & (ALIGNMENT - 1)); /* XXX: could overflow */
  if (n <= avail) { avail -= n; return space + avail; }
  x = malloc(n);
  if (!x) errno = ENOMEM;
  return x;
}
 
void alloc_free(void *x) 
{
  if (x >= space)
    if (x < space + SPACE)
      return; /* XXX: assuming that pointers are flat */
  free(x);
}
 
int alloc_re(void **x,unsigned int m,unsigned int n) 
{
  char *y;
 
  y = alloc(n);
  if (!y) return 0;
  byte_copy(y,m,*x);
  qfree(*x);
  *x = y;
  return 1;
}